This invention relates to scraper devices for scraping the surface of a vessel. The scraper device and system according to the invention are particularly adapted for scraping the surfaces of a vessel in which a foodstuff is cooked or cooled.
Foodstuff cooking operations commonly apply cooking heat to a foodstuff through the surfaces of a vessel in which the foodstuff is contained. Because the vessels may be large in commercial cooking operations and because the heat is applied only through the vessel walls, commercial cooking devices commonly include a mixing or agitating structure that continuously agitates the material in the vessel during the course of cooking. These agitating arrangements are necessary to produce even cooking throughout the material in the vessel and speed up the cooking process.
However, mixers or agitators in the cooking vessel are sometimes insufficient to prevent foodstuff from cooking or burning onto the vessel walls through which heat is applied. Where the foodstuff being cooked does cook or burn onto the vessel walls, special scraping devices may be used within the vessel to periodically scrape across the surfaces of the vessel through which heat is applied and remove any buildup.
Scraping devices may also be required to periodically scrape the surfaces of a vessel in which a foodstuff is being cooled rather than cooked. In the case of a vessel used to cool a foodstuff, the foodstuff may tend to stick to the surfaces of the vessel and inhibit the cooling operation. Scrapers are required in these instances to remove the material sticking to the vessel surfaces and allow the remaining material to be cooled more effectively.
U.S. Pat. No. 4,733,607 discloses a device commonly referred to as a jacketed blender which may be used in commercial cooking or cooling operations. A jacketed blender includes one or more roughly semicircular troughs each surrounded at least partially by a jacket through which a heating or cooling material may be circulated. Each trough includes a separate agitator device. The respective agitator is rotated about its longitudinal drive axis to agitate the material in the trough and thereby allow the device to apply or remove heat more evenly to the material in the trough and thus provide more even cooling or cooking. U.S. Pat. No. 4,733,607 shows helical agitating members commonly referred to as ribbons. Paddles or other agitating structures may also be employed for the purpose of mixing or agitating the contents of the vessel during the cooking or cooling process.
The particular jacketed blender shown in U.S. Pat. No. 4,733,607 also includes a number of scrapers mounted at different points along the length of each agitator ribbon. Each scraper includes a block of material having a flat bottom surface with steep front and back sides that intersect with the flat bottom surface to form front and back scraping edges. In one embodiment shown in the patent, the scraper blocks are each mounted on a post extending from the ribbon generally parallel to the ribbon drive axis. In an alternative arrangement shown in U.S. Pat. No. 4,733,607, each scraper block is connected to the respective ribbon through an elongated flat member extending transversely from the ribbon. The elongated flat support is configured to twist from side to side about the support""s longitudinal axis and to flex along a line extending perpendicular to the vessel surface. The scraper block is connected to the end of this elongated flat member. In both embodiments, the supports for the scraper blocks place one or both scraping edges in contact with the vessel surface so that one edge scrapes across the vessel surface as the agitator ribbon is driven about its longitudinal drive axis. The front and back scraping edges allow the scraper block to provide the scraping action against the vessel surfaces regardless of the direction in which the agitator ribbon is rotated.
One problem with the scraper block shown in U.S. Pat. No. 4,733,607 is that the scraping edges tend to wear over a relatively short period of time to produce a rounded surface that extends between the flat bottom surface and steep side surface. This rounded surface produces an ineffective scraping action against the vessel wall and requires that the scraper block be replaced. Replacing the scraper blocks adds significantly to operating costs due to the cost of new scraper blocks and cost of labor associated with changing out the scraper blocks. Perhaps more importantly, the device must be taken out of service in order to change the scraper blocks and thus these types of scraper blocks can decrease productivity. Furthermore, wear in the scraper blocks causes the device to produce an inconsistent product especially when the device is used to cook a foodstuff. More particularly, as the scraper blocks wear and thus become less effective at scraping the surfaces of the vessel, the foodstuff will cook-on or burn-on more to the vessel surfaces and much of this burnt-on or cooked-on material is eventually mixed with the remaining foodstuff, changing the character of the final product. When the scraper blocks are new, the cooked foodstuff will contain relatively little of the burnt-on or cooked-on material. However, the final product will include more and more of this burnt-on or cooked-on material as the scraper blocks wear.
Other problems with the type of scraper shown in U.S. Pat. No. 4,733,607 relate to the manner in which the scraper block is connected to the ribbon element. The connection includes small openings that can trap foodstuff in the course of operations, and making the scrapers unsanitary. Also, as the agitator element rotates in the vessel, the contact between the scraper block and the vessel surface together with the contact between the scraper block and the material being cooked in the vessel place a good deal of force on the scraper block in a direction opposite to the direction that the scraper block is driven. This force is ultimately transferred to the ribbon through the base of the post or member on which the scraper block is mounted. Depending upon the nature of the foodstuff being cooked and the speed at which the ribbon is rotated, the torque applied to the ribbon material through the scraper support post or flat support member may be substantial and may cause significant deflections in the ribbon material which may ultimately lead to fatigue in the ribbon material. Deflection in the ribbon material also causes the scrapers to apply force unevenly to the vessel surfaces and produces rapid wear at certain points in the scrapers and excessive wear in the vessel walls.
The present invention includes both a scraper device and a scraper system employing the scraper device. The scraper device includes a fixture or scraper fixture which is adapted to be placed in a working position adjacent to a surface to be scraped. At least one flex arm is connected at its proximal end to the scraper fixture and includes a distal end extending from the fixture toward the surface to be scraped when the scraper fixture is in the working position. A scraper plate is located at the distal end of the flex arm and extends at an acute scraping angle with respect to the surface to be scraped when the fixture is in the working position. In this position, a scraping edge of the scraper plate makes contact with the surface to be scraped. The shallow angle between the scraper plate and surface to be scraped, combined with the flexible nature of the flex arm and loading on the flex arm when the scraper fixture is in the working position combine to produce a robust and effective scraping action between the scraper plate and the surface to be scraped as the scraper fixture moves laterally relative to the surface. Although a scraper according to the present invention is highly effective at scraping the desired surface, the flexible nature of the flex arm and the angle between the scraper plate and surface to be scraped combine to produce a relatively gentle scraping action that does not produce undue wear to the surface to be scraped.
A scraper system according to the present invention includes at least one scraper device and a support for supporting the scraper fixture of the device in the working position with respect to the surface to be scraped. The support may be associated with a mixing or agitating element, such as the ribbon of a ribbon agitating structure, or may be separate from any agitating device. In either case, one preferred form of the invention includes one and preferably several scraper devices that extend along substantially the entire length of the vessel to be scraped. These long scraper devices each produce a complete scraping of the vessel on each revolution of the support structure and may allow the support structure to be driven more slowly while still preventing undesirable sticking at the heat transfer surfaces of the vessel.
Preferred forms of the invention include two flex arms, a first flex arm extending along a device movement axis from one side of the fixture and an additional or second flex arm extending from the opposite side of the scraper fixture along the device movement axis. Each flex arm includes a respective scraper plate extending at a respective acute angle to the surface to be scraped with a respective scraping edge contacting the surface to be scraped when the scraper fixture is held in the working position. With both scraper plates extending at an acute angle to the surface to be scraped, the scraper device may be configured to include a relatively deep concave relief area defined between the opposing scraping edges. This is in contrast to the flat bottom of the scraper block shown in U.S. Pat. No. 4,733,607. The flex arms and respective scraper plates located on opposite sides of the scraper fixture along the device movement axis allow this preferred form of scraper device to be driven in either direction along the device movement axis to provide the desired scraping action.
The scraper fixture may include upper and lower clamping surfaces that hold the flex arm or flex arms at a desired angle with respect to the surface to be scraped. Because a preferred scraper device includes first and second flex arms on either side of the device, the scraper fixture may be thought of as having a first set of upper and lower clamping surfaces on one side for holding the first flex arm and a second set of upper and lower clamping surfaces on the opposite side for holding the second flex arm.
Each flex arm and respective scraper plate may be formed from a common sheet or plate of material. Also, both the flex arms and respective scraper plates in forms of invention including two sets of such components may be formed from a common sheet or plate of material. Where the scraper device includes two oppositely extending flex arms formed from a common plate of material, the upper and lower clamping surfaces of the scraper fixture may include a curve which impresses a curvature on a central portion of the plate. This curvature in the plate material positions the flex arms so that they extend at the desired angle downwardly toward the surface to be scraped.
The scraper device according to the invention may be connected to a post or flexible member extending laterally or transversely from an agitator ribbon similar to the scraper blocks shown in U.S. Pat. No. 4,733,607. Alternatively, the scraper device may be connected to a support which is welded or otherwise formed in the agitator element. In this preferred form of the invention, and where the agitator element comprises a ribbon of material, the fixture extends on both sides of the ribbon material along a longitudinal axis extending transverse to the ribbon. The fixture is preferably centered on the ribbon so that substantially equal forces are applied to the fixture as the ribbon is driven about its drive axis. This equalization of forces on either side of the ribbon material substantially eliminates any bending or deflecting in the ribbon material occasioned by the forces applied to the scraper device as the device is driven in a scraping operation.
In some forms of the invention the forces applied to the scraper device as the device is moved through the material within the vessel may be reduced by configuring the flex arm as a number of separate members spaced apart along the longitudinal axis of the scraper device. The openings between the separate members making up the flex arm effectively reduce the profile of the scraper device and in so doing reduce the force applied to the scraper as it is driven through the material in the vessel.